Improvement in straight-edges



@uiten glatte geg-stent @frn sAMUEL DARLING, `o F BANGOR, MAINE.-

4Leim-s Patent No.' 73,082, @faz Tammy 7, 186s.

IMPROVEMENT IN STRAIGHT-EDGES.

itin Stlgrhulr maar tr in' tlgrse rttcts atmt zint-making pitt nt 111etime.

TO 'ALL WHOM IT MAY CONCERN:

Be it known that I, SAMUEL DARLING, of Bangor, inthe county vofPenobscot, and State ofMaine, have invented certain Improvements inStraight-Edges; and I do hereby declare that the following, taken `inconnection with the drawings which accompany and form part of thisspecification, is a description of my invention suicicnt to enable thoseskilled in the art topractise it.

The object of my invention is the production of a tool orimplement,'usually designated by machinists and artisans, astraight-edge, which shall have greater durability and toughness, lessliability to be fractured or bruised, andgreatcr hardness at its edgesthan any heretofore known or used, and which shall, also, when made witha graduated scale thereon, to serve as a rule or measure, insure greataccuracy and reliability in' such scale, as well throughout its lentirelength, as also for each of its aliquot parts into which it may bedivided and subdivided. l l' Straight-edges, as heretofore made, havebeen usually formed from steel or other metal which is of homogeneous'character and hardness throughout. If this be a soft metal, theimplement, from its frequent handling and being left about, and throwndown upon the' benches amongst other metal articles or tools, isconstantly liable to 'become indented or nicked at it edges and corners,until soon it becomes Aso injured and untrue as to be valueless.

If, in order to avoid these liabilities'todamage, it be made of hardermaterial, such as hardened 'plate-steel,I and of homogeneous characterand texture throughout, it is in such case, by reason of its brittlenature, in

constant'danger ot' being fractured or broken, and inleither caserendered useless.

Such tools being frequently broken, and even from slight blows andshocks, torwhich, in a machine-shop, they are constantly subject, it is,even as a mere matter of economy only, highly important to provide 'astraighti edge, which, whilst possessing at its edges the requisitedegree of hardness for all purposes for'which it may'be used, shall atthe same 'time have its mass or body, except at or near the edges, ofsuch character or texture as to be but little, if any, liable tofracture, indentation, cr abrasion, and thus serve'to preserve theentire instrument for along period in eliicient working condition. Sucha straight-edge forms thesubject of my presentinvention.

Figure 1, ofthe accompanying sheet of drawings, represents my improvedstraight-edge, with a scale graduated thereon in the manner hereinafterdescribed, and after the same has been polished, ready fo'ruse; and

Figure Zreprcsents the same, after the edges thereof have been hardened,but before the surface has been ground or polished.

Figures 3, 4, and 5, represent modiclations and cross-sections ofthesaine.

In making my improved straight-edge, I take a pieee of steel plate, ofthe length, breadth, a'nd thickness desired, and heat it to a propertemperature and dip it into water; but before so heating anda dippingit, I confine the plate between two bl'ocks of iron, and-in order tolimit the eifects'of the hardening-processtothe edges only, I allow theedges so to be hardened, to project beyond the said conining-blocks. Thetwo blocks and the interposed plate are then heated together, and whilethe blocks serve to prevent the contact of the water with the heatedplate, except at its projecting edges, they also serve t0 keep up'thetemperature of the centre of'the plate, so that it does not cool sorapidly as to become brittle. Thesame result may be attained bytempering or hardening the edges by pressure between surfaces of coldiron, leaving the centre unchanged. After being thustempered, thc plate,it warped, as it is apt to be by the tempering-process, isA renderedtrue by hammering,`

and its edges ground straight and smooth, the opposite onesbeing madeparallel.

A straight-edge cannot long remain accurate when its edges are soft, andeasily worn or indented; but if the whole plate be hardened alike,besides being in such case brittle, it becomes very much warped andtwisted, and being in this state very refractory, these warps and twistsdo not admit of being hammered out. By my improvement, however, theedges alone being hardened, the whole plate admits of being hammered onthe sides to remove the warps and twists incident to thehardening-process.

My manner of obtaining the correct graduation of the hardenedstraighteedge is as follows: I find by experiment that the edges will,in the hardening-process, expand about one twenty-fifth (315) afan inchto the foot. I therefore eut and graduate them, before hardening theedges accurately, to one twenty-fifth of an inch to the foot short ofthestandard measure.

In preparing and hardening the edges of a number of plates, it is found,however, that they will not all expand alike. I, however, make them allalike at first, and afterwards bring or reduce each one to the exactstandard, by drawing the temper. In'order to do this, theymust all bemade long enough to permit this reducv Vtio/n or shortening. To effectthis, I use a hot bath of oil or tallow, and the more the straight-edgeneeds to be shortened, the hotter the bath must be. The degree of"l heatnecessary for this purpose must be learned by,4

practice. If one edge be longer than the other, then that edge alonemustbe p'ut into the bath, until it be brought. down tothe true standard ofthe other; andthe edge not so being heated may be clamped with metalwhen necessary to kleep it from heating.

It is apparent from the above that either or both edges, as the case4may require, and to a greater or less extent, may be contracted, untilthe precise desired standard be obtained.

It is oi'ten necessary or desirable to have a straight-edge of greatlength, even to the extent of twenty feet or thereabouts. To make such aone in a single piece would be verydiiiicult and inconvenient, if notimpracticable, I therefore make it'in sections, of, say, fourstraight-edges, each five feet long, andeach with ',hardcned edges, madeas above described; 'and after iii-st making in each two or more slots,in a direction transverse of their lengths, for the reception of screws,I aiiix these sections, placed end to end, by meanspf screws, to a wide,well-seasoned board, and secure them in position, so that their hardenededges shall be in a-continuous straight line and in order to true theseedges before finally -securing them in position, I make use of anotherstraight-edge to true them by. The screws and slots admit also ot'readjustment of the whole at any time, if by accident or otherwise theparts get displaced or out of true, or if the wooden base should springby seasoning, tc. Instead oi' a board as such foundation or support forthe several section of hardened straight-edges, a sheetef metal may beused.

'i'o make a hardened straight-edge of six feet in length, I would aiiixtwo pieces, three feet each in length, to a six-feet soft metal-plate,and then true them by a four-feet straight-edge. An edge nearer straightand more reliable-for one of this length,-could bc obtained in this waythan by making it in a single piece; whilst it also, as in the stilllonger ones above' mentioned, would have the additional advantage ofbeing readily adjustable when out of true. This modeof construction isillustrated in iig. 3.

It is also important for some purposes to have thicker straight-edgesthan can be conveniently hardened in the manner above described. Suchstraight-edges are generally made from' one-quarter to one-half inch inthickness, and are called by machinists winders, which name willindicate one of the uses to which they are applied. |Ihey must be thickenough to stand irinly upon their edges.

To make a thick straight-edge, therefore, which `shall'enabodyV thedistinguishing characteristic feature of extreme hardness ofthe edges,in excess of that between the edges, I put two or more hardenedstraight-edges,

of medium thickness, say from an eighth to thrce-sixteenths of an inchthick, together, by riveting, or any of 1 the known methods of doingsuch work, and then finish it as one piece, or I attach a thin hardenedstraightedge to a thick, unhardened one, or upon any suitablefoundation.

It is desirable that thick straight-edges should have one thin edge, andthey are generally so constructed so that they can be applied' withgreater accuracy to the'work. 'lo accomplish this in making thickstraightedges, as ab'ove described, where two or more pieces are pnttogether, one of the pieces may be wider, and thinner if desirable, thanthe other or others. In attaching a thin vstraight-edgeto anyfoundation, as above described, the hardened edge may project beyond thepiece to which it is attached, to serve as a thin edge, While,theopposite edge of bot'il pieces may be used when it is applied as aWinder.

' These graduated and hardened straight-edges, as above described, areof great advantage 'and utility when clamped together and used as a.gauge for gauging wire, Ste., or instead of graduating the hardenededges, an unhardened bevelled or plain pi-ece may be graduated andattached to the hardened piece. Such a formed gauge is much used bywatchmakers and othermechanics, but they have not heretofore beenhardened as above described, and consequently they soon wear out oftrue. Both plans of constructing this gauge are represented in iig. 5.The'side or part A represents it as constructed withagraduatediunhardened piece, attached to an ungraduated hardened piece;and the side or part B represents it as constructed with the graduatedhardened straight-edge only. i

1. I claim a straight-edge, hardened at its edge or edges, and not atits centre, substantially as described.

2. I claim a straight-edge, having a hardened edge or edges, andadmitting, when warped by hardening, of being brought into true,substantially as described.

3. I claim a straight-edge, made of two or more thin pieces, having oneor both edges hardened, for the purpose of making itthicker,substantially as described.

4. I claim a straightedge,composcd of a thin plate, with hardened edgeor edges, and a supporting-bed or plate, substantially as described. l

5. I claim a straight-edge, composed of two or more hardenedstraighbedgcs, secured end to end, upon a supporting bed-plate.

6. I claim a straight-cdge, when constructed as herein set forth,whether the same be used as a single -edge or 'with two opposing edges,as in a gauge, substantially as described. l

7. Iclaim the mode herein described of under-graduating thestraight-edges, to compensate for the stretch in hardening.

8. I claim the process herein described of reducing the graduated edgesto the proper Standard by tempering.

SAMUEL DARLING.

Witnesses:

JOHN E. HALL, ALBERT W. PAINE.

